Typical drilling operations in underground mines use a drill head including a socket adapted to receive a proximal end of a drill steel and thus impart rotary driving force for forming a borehole. Unlike a conventional handheld drill with an integral, adjustable chuck, the socket is typically a fixed dimension structure, and adapted to work in connection with a removable chuck designed to withstand the significant driving forces and harsh operating conditions. Thus, thus the drill steel must be specially adapted (e.g., have a particular shape and size) to fit in a particular chuck, or else it will potentially loosen during the drilling operation (and particularly, during withdrawal of the drilling steel from the borehole once formed).
In the past, others have proposed so-called “twist lock” systems, whereby a steel can be inserted in the chuck and twisted to achieve a selectively locked configuration (see, e.g., U.S. Pat. No. 4,226,290, the disclosure of which is incorporated herein by reference). While this system works for its intended purpose, it cannot reliably accommodate different sizes of steels beyond a certain range, such as ones with a smaller maximum diameter, or those without twist lock capabilities. In the situation where a twist lock arrangement is not present (e.g., a hex receiver and a hex drill steel), the driving for purposes of drilling the borehole might proceed unfettered, but the operator must then exercise considerable care in withdrawing the steel from the borehole. This is typically done by slowing the rotation and withdrawal speed, both of which contribute to a lack of efficiency. The twist lock arrangement also requires providing a drill steel, which is a wear part, with a costly forged end to form the engagement, which is disadvantageous for obvious reasons.
Accordingly, a need is identified for a system whereby a variety of different sizes and shapes of drill steels or other drillings tools, such as bolts, may be accommodated by a single drill head without hindering the efficiency of the drilling operation. In particular, the arrangement would enhance the flexibility of the operation by allowing for the use of a variety of tools with a single chuck, and also promote efficiency by ensuring that a secure locking engagement is established using conventional “off the shelf” components that need not be modified in any way. Significant reductions in costs would result from the enhancements afforded.